Blends of vinyl chloride polymer and hydrocarbon elastomer containing graft copolymer as compatibilizer



United States Patent 3,312,756 BLENDS OF VINYL CHLORIDE POLYMER ANDROCARBON ELASTOMER CONTAINING GRAFT COPOLYMER AS COMPATIBILIZER MassimoBaer, Longmeadow, and Ernest H. Hankey, Springfield, Mass., assignors toMonsanto Company, St. Louis, Mo., a corporation of Delaware No Drawing.Filed June 6, 1966, Ser. No. 555,271 9 Claims. (Cl. 260-876) The presentinvention rel-ates to blends of thermoplastic polymers and moreparticularly to blends of a rigid vinyl chloride polymer and ahydrocarbon elastomer. This application is a continuation-in-part of thecopending application Ser. No. 256,272, filed Feb. 5, 1963, allowed .onMay 6, 1966, and now abandoned, which in turn is a division ofapplication Ser. No. 800,911, filed Mar. 23, 1959, now US. Patent3,085,082.

It is known that blends of rigid vinyl chloride polymers and certaindiene elastomers which contain polar groups in their chemical structurehave desirable physical properties. In particular, polymer blendscontaining 80-95% of the vinyl chloride polymer and, correspondingly,205% of the diene elastomer are easily processed and have considerablyhigher impact strength than the rigid vinyl chloride polymer includedtherein. Such polymer blends are useful in the fabrication of rigidshock resistant items such as pipe, tubing, sheets, and the like.Polymer blends containing larger quantities of the elastomer, e.g.,l080% of the vinyl chloride polymer and, correspondingly, 90-20 parts ofthe diene elastomer, are tough flexible materials which resemble rubberand/ or plasticized vinyl chloride polymers in properties, but havecertain definitely superior properties as compared with either rubber orconventionally plasticized vinyl chloride polymers. The diene elastomersincluded in the above described polymer blends contain in their chemicalstructure polar groups such as chloride atoms, ester groups, nitrilegroups and the like. Typical of the diene elastomers employed arepolychloroprene, butadiene-acrylonitrile copolyrners, butadiene-methylisopropenyl ketone copolymers, butadiene-vinyl pyridine copolymers,butadiene-ethyl acrylate copolymers, etc.

Although blends of rigid vinyl chloride polymers and nonpolarhydrocarbon elastomers such as natural rubber, polybutadiene,styrene-butadiene rubbers, polyethylene and the like are known, thesepolymer blends do not have physical properties which correspond to thoseof the polymer blends described in the paragraph above. In particular,such blends of vinyl chloride polymers and the nonpolar hydrocarbonelastomers tend to be weak and cheesy. Obviously, it would be desirableto have available to the art means for preparing polymer blends of goodproperties from rigid vinyl chloride polymers and nonpolar hydrocarbonelastomers.

It is an object of this invention to provide novel polymer compositionshaving good properties and which include therein a rigid vinyl chloridepolymer and a nonpolar hydrocarbon elastomer.

Other objects and advantages of this invention will be apparent from thefollowing detailed description thereof.

The above and related objects are attained by preparing compositionsconsisting essentially of an intimate fusion blend of (1) a rigid vinylchloride polymer, (2) a nonpolar hydrocarbon elastomer, and (3) a minorbut effective quantity of a third component which renders a rigid vinylchloride polymer and the nonpolar hydrocarbon elastomer more compatibleand improves the physical properties, especially the impact strength, ofthe polymer blend. In the subsequent description of this invention, thethird component of the polymer blend will be referred to as acompatibilizing agent. The comgraft copolymers prepared by polymerizing10-200 and preferably 20-80 parts by weight of specified monomermixtures in an aqueous dispersion containing parts by weight of arubbery diene polymer. The specified monomer mixtures employed in thepreparation of the graft copolymers comprise monovinylidene aromatichydrocarbons and nitriles selected from the group consisting ofacrylonitrile, methacrylonitrile and mixtures of the same. The polymerblends of this invention are prepared by subjecting the rigid vinylchloride polymer, the nonpolar hydrocarbon elastomer and thecompatibilizing agent to an intensive mixing action at an elevatedtemperature.

The following examples are set forth to illustrate more clearly theprinciple and practice of this invention to those skilled in the art.Where parts or quantities are mentioned, they are parts or quantities byweight.

Unless otherwise noted, all of the polymer blends subpatibilizing agentsare sequently reported in the examples are prepared by the followingstandard procedure. The vinyl chloride polymer and a stabilizertherefore are worked on a 2-roll rubber mill until a rolling bank isformed. Thereafter, the compatibilizing agent, the nonpolar hydrocarbonelastomer and any additional components such as lubricants, fillers,etc., are added on the mill and the resulting mixture is worked for theperiod of time indicated in the examples. The roll temperatures aremaintained at 340 F. throughout the mixing operation. The polymer blendsare heated for 4 minutes at C. and then compression molded for 1 minuteat 185 C. under a pressure of 4,000 psi. to prepare test specimens formeasurement of physical properties.

EXAMPLE I A blend of 95 parts of a vinyl chloride homopolymer, 5 partsof polyethylene and 2 parts of a tin stabilizer is milled for 25 minutesto prepare a control blend. This control blend has an Izod impactstrength of only 1.5 ft. lbs./inch of notch.

The vinyl chloride resin included in the above blend is a commerciallyavailable vinyl chloride homopolymer which has a specific viscosity ofabout 0.48 as measured in an 0.4% solution in cyelohexanone at 25 C. Thepolyethylene included in the blend has a number average molecular weightof about 25,00030,000 and a density of about 0.9l60.9l7.

EXAMPLE II Part A Four polymer blends are prepared having thecomposition and physical properties set forth in Table I.

TABLE I Blend Identification Component:

Vinyl chloride resin Polyethylene 5 Polypropylene Styrene-acrylonitrilegraft copolymer Dibutyl tin dilauryl mercaptide Stearic acid Physicalproperties: 1

llmptclt1 strength at 25 C. it. lbs/inch n e Tensile strength at yield,p. Percent elongation at yield Modulus at yield X 10 p.s.i

1 All properties measured by current ASTM methods. 2 Measured with anotch having a radius of curvature of 0.010.

The vinyl chloride resin, and polyethylene elastomer included in theblends are the same polymers described in Example I. The polypropyleneelastomer in an atactic (amorphous) polymer having a molecular weightofabout 40,000. The styrene-acrylonitrile graft copolymer is prepared bypolymerizing 28 parts of styrene and 12 parts of acrylonitrile in alatex containing 100 parts of polybutadiene.

As earlier noted, the compositions of this invention comprises anintimate fusion blend of (a) a rigid vinyl chloride polymer, (b) anonpolar hydrocarbon elastomer that is normally incompatible with saidrigid vinyl chloride polymer, and (-c) a compatibilizing agent thatenhances the compatibility of the rigid vinyl chloride polymer and thenonpolar hydrocarbon elastomer.

The proportions of the rigid vinyl chloride polymer and the nonpolarhydrocarbon elastomer to be included in the polymer blends will dependprimarily upon the properties desired in the blend. Where hard rigidmaterials suitable for use in the manufacture of pipe and similar itemsare desired, the polymer blends will contain about 70-98 parts of therigid vinyl chloride polymer and, correspondingly, about 30-2 parts ofthe nonpolar hydrocarbon elastomer. Rigid polymer blends of optimumproperties will contain 80-95 parts of the rigid vinyl chloride polymerand, correspondingly, 20-5 parts of the nonpolar hydrocarbon elastomeror more especially 85-95 parts of the rigid vinyl chloride polymer and,correspondingly, 15-5 parts of the nonpolar hydrocarbon elastomer. Itwill be understood, of course, that the particular proportions of thetwo polymers to be included in such rigid polymer blends will besomewhat dependent upon the nature and characteristics of the individualpolymers employed therein. Where elastic, rubbery and/ or leather-likematerials are desired, the polymer blends may contain about -79 parts ofthe rigid vinyl chloride polymer and, correspondingly, about 90-21 partsof the nonpolar hydrocarbon elastomer.

The quantity of the compatibilizing agent included in the polymer blendwill be sufficient to enhance the compatibility of the rigid vinylchloride polymer and the nonpolar hydrocarbon elastomer. The minimumquantity required for this purpose Will depend somewhat upon theparticular compatibilizing agent employed, but can be establishedthrough routine experimentation. Specifically, to determine the minimumquantity of the compatibilizin-g agent required, the blend of the rigidvinyl chloride polymer, the nonpolar hydrocarbon elastomer and thecompatibilizing agent should be worked for minutes on a 2- roll rubbermill with the roll temperatures being maintained at 340 F. The resultingblend then should be compared with a similarly worked control blend thatcontains no compatibilizing agent. In the case of blends con taining atleast 70 parts of the rigid vinyl chloride resin and less than 30 partsof the nonpolar hydrocarbon elastomer, the blend containing thecompatibilizing agent will have a higher Izod impact strength. Thequantity of the compatibilizing agent employed should be such that theimpact strength of the blend containing the compatibilizing agent is atleast 0.5 ft. lbi/inch of notch higher than the impact strength of thecontrol blend. In the case of blends containing less than 70 parts ofthe rigid vinyl chloride polymer and more than 30 parts of the nonpolarhydrocarbon elastomer, the blend containing the compatibilizing agentwill have a higher elongation at yield. In most cases, thecompatibilizing agent will constitute 1-10 or preferably 2-8% by weightof the blend.

The vinyl chloride polymer included in the polymer blends may be anyrigid vinyl chloride polymer such as vinyl chloride homopolymers andinterpolymers of vinyl chloride with interpolymerizable monomers such asvinyl esters of organic acids containing 1-18 carbon atoms, e.g., vinylacetate, vinyl stearate, etc.: vinylidene chloride; acrylonitrile;methacrylonitrile, alkyl ac-rylate esters in which the alkyl groupcontains 1-8 carbon atoms, e.g., methyl acrylate and butyl acrylate; thecorresponding alkyl methacrylate esters; dialky-l esters of dibasicorganic acids in which the alkyl groups contain 1-8 carbon atoms, e.g.,dibutyl fumarate, diethyl maleate, etc. In general, where vinyl chlorideinterpolymers are employed, they should contain at least about weightpercent of vinyl chloride. To obtain optimum properties in the polymerblends, the vinyl chloride polymer included therein should have arelatively high molecular weight, e.g., the polymers should have aspecific viscosity of at least about 0.4 as determined in an 0.4 weightpercent solution in cyclohexanone at 25 C.

The nonpolar hydrocarbon elastomer included in the polymer blend may beessentially any thermoplastic hydrocarbon polymer or mixtures thereofthat has an elongation at break of at least 5% and that is essentiallyfree of polar substituents such as halogen atoms, ester groups, amidegroups, amine groups, nitrile groups, hydroxyl groups, carboxyl groupsand the like. One class of such nonpolar hydrocarbon elastomers consistsof homopolymers of alpha-olefines such as ethylene, propylene,isobutylene and the like, interpolymers consisting solely of two or moresuch alpha-olefins and interpolymers of at least by weight of such analpha-olefine with up to 15% by weight of an interpolymerizablevinylidene monomer such as vinyl chloride, vinylidene chloride, vinylacetate, alkyl acrylate esters such as methyl acrylate and butylacrylate, the corresponding alkyl methacrylate esters, styrene,alpha-methylstyrene, ring-alkyl substituted styrenes, butadiene,isoprene and the like. Another class of suitable nonpolar hydrocarbonelastomers consists of homopolymers of acrylic conjugated 1,3-dienessuch as butadiene, isoprene,2,3-dimethylbutadiene, piperylene and thelike and interpolymers of such conjugated dienes which contain at least50% by weight of the conjugated diene. The comonomers included in suchconjugated diene interpolymers preferably are hydrocarbon monomers suchas styrene, alpha-methylstyrene, ring-alkyl substituted styrenes and thelike. In some cases, if desired, the rubbery diene interpolymer maycontain up to about 10% by weight of a vinylidene monomer containing apolar substituent such as a halogen atom, an ester group, an amidegroup, an amine group, a nitrile group, a hydroxyl group, a carboxylgroup or the like. Typical examples of such polar monomers includeacrylonitrile, methacrylonitrile, alkyl acrylate esters such as methylacrylate and butyl acrylate, the corresponding alkyl methacrylateesters, vinyl acetate, acrylic acid, methacrylic acid, acrylarnide,methacrylamide, vinylidene chloride, vinyl pyridine, ring-alkylsubstituted pyridines and the like.

The compatibilizing agents used in the polymer blends are graftcopolymers prepared by polymerizing 10-200 and preferably 20-80' partsby weight of specified monomer mixtures in an aqueous dispersioncontaining 100 parts by weight of a rubbery diene polymer. The monomermixtures employed in the preparation of the graft co polymers comprise10-90% by Weight of either aorylonitrile or methacrylonitrile and,correspondingly, -10% by weight of a monovinylidene aromatichydrocarbon. Typical of the monovinylidene aromatic hydrocarbon monomersthat may be employed in the above monomer mixtures are styrene;ring-substituted alkylstyrenes, e.g., 2,4-dimethylstyrene,p-ethylstyrene, etc.; ring-substituted halostyrenes, e.g., o-, m-, andp-chlorostyrenes, 2,4-dichlorostyre'ne, etc.: ring-substituted a1kyl-,ring-substituted halostyrenes, e.g., 2-methyl-4-chlorostyrene, etc.; ormixtures of such monovinylidene aromatic hydrocarbons, which mixturesmay include a monovinylidene aromatic hydrocarbon compound which, byitself, will not readily interpolymerize with acrylonitrile or alkylacrylate esters, e.g., alpha-methylstyrene.

The rubbery diene polymers on which the above described monomer mixturesare polymerized may be essentially any polymer of an acyclic conjugated1,3-diene having a second order transition temperature below 0 C. andpreferably below -20 C. The preferred diene polymers for this purposeare homopolymers of butadiene, isoprene, 2,3-dimethylbutadiene,piperylene, and the like or interpolymers of at least 50% by weight ofsuch a diene with an interpolymerizable vinylidene monomer such asstyrene, acrylonitrile, alkyl acrylates such as methyl acrylate, andbutyl acrylate and the like. It is frequently desirable to include asmall quantity e.g., 0.53.0% by weight of a polyunsaturated monomer suchas divinyl benzene or diallyl maleate in the rubbery diene polymer.

Methods for preparing graft copolymers of the above types are wellknown. See for example US. 2,802,809 and the copending application ofMassimo Baer, S.N. 706,543, filed Jan. 2, 1958, now abandoned.

In addition to the rigid vinyl chloride polymer, the nonpolarhydrocarbon elastomer and the compatibilizing agent, the polymer blendsof this invention ordinarily will contain conventional stabilizers andanti-oxidants of the type employed with vinyl chloride polymers. Ifdesired, colorants, lubricants, pigments, fillers, etc., also may beincluded in the polymer blends.

The rigid vinyl chloride polymer, the nonpolar hydrocarbon elastomer andthe compatibilizing agent may be blended together by being worked onconventional plastics working equipment such as rubber mills, Banburymixers, extruders, etc. The blends should be worked at a temperatureabove that at which the vinyl chloride polymer fuses to obtain anintimate well fused blend. Temperatures m'thin the range of about300-370 F. are normally employed. If desired, it is also possible toprepare an aqueous dispersion of the three components, e.g., by mixinglatexes of the vinyl chloride polymer and the nonpolar hydrocarbonel-astomer and incorporating the compatibilizin-g agent in the mixedlatexes, and then coagulating and/or drying the dispersion to recover ablend of the three components. After the mixed polymers are recovered bythis procedure, it is still necessary to heat the mixture for a shorttime while comalaxating the composition on some type of plastics workingequipment.

The preferred polymer blends of the invention are those in which thenonopolar hydrocarbon elastomer is a polymer of an alpha-olefine such asethylene and particularly polyethylene. These polymer blends, inaddition to having excellent physical properties, have outstandingresistance to oxidation and/or ultra-violet light. For this reason, suchpolymer blends are well adapted to be employed in the manufacture ofarticles which will be exposed to air and/or sunlight for extendedperiods of time.

The polymer blends of the invention can be molded, calendered orextruded into diverse shapes and forms such as rods, tubes, sheets,films, filaments, etc., by techniques well known in the polymer art. Therigid polymer blends, i.e., those containing at least 70% by weight ofthe rigid vinyl chloride polymer, have utility in many fields wherevinyl chloride polymers of high impact strength are desired andespecially in the manufacture of plastic pipe. The flexible polymerblends, i.e., those blends containing more than 30% by weight of thenonpolar hydrocarbon elastomer, have utility as an electrical cableinsulation material, as a film in the manufacture of shower curtains andsimilar items, etc.

The above descriptions and particularly the examples are set forth byway of illustration only. Many other variations and modificationsthereof will be obvious to those skilled in the art and can be madewithout departing from the spirit and scope of the invention hereindescribed.

What is claimed is:

1. A composition of matter comprising an intimate fusion blend of -98parts by weight of a rigid vinyl chloride polymer, said vinyl polymercomprising at least 80% by weight vinyl chloride and correspondingly,90-2 parts by weight of a non-polar hydrocarbon elastomer selected fromthe group consisting of homopolymers of alpha-monoolefines,interpolymers of at least two alpha- Inonoolefines; interpolymers of atleast 85% by weight of an alpha-monoolefine and up to by weight of aninterpolymerizable vinylidene monomer; homopolymers of acyclicconjugated 1,3-dienes; and inter-polymers of at least 50% by weight ofan acyclic'conjugated 1,3- diene, up to 50% by weight of a hydrocarbonmonomer selected from the group consisting of styrene, alpha-methylstyrene and ring-alkyl substituted styrenes, and up to 10% :by weight ofa vinylidene monomer having a polar substituent, said non-polarhydrocarbon elastomer normally being incompatible with said rigid Vinylchloride polymer; said composition also containing from about 1-10% byweight of graft-copolymer prepared by polymerizing 10-20'0 parts byweight of a monovinylidene aromatic hydrocarbon and a nitrile selectedfrom the group consisting of acrylonitrile, methacrylonitrile andmixtures thereof in the presence of 100 parts by weight of a rubberydiene polymer having a second order transition temperature below about 0C., said graft copolymer being sulficient to enhance the compatibilityof the rigid vinyl chloride polymer and the non-polar hydrocarbonelastomer.

2. A composition of matter comprising an intimate fusion blend of -95parts by weight of a rigid vinyl chloride polymer, said vinyl chloridepolymer comprising at least by weight vinyl chloride andcorrespondingly, 30-5 parts by weight of a non-polar hydrocarbonelastomer selected from the group consisting of homopolymers ofalpha-monoolefines, interpolymers of at least two alphamonoolefines;interpolymers of at least by Weight of an alpha-monoolefine and up to 15by weight of an interpolymerizable vinylidene monomer; homopolymers ofacyclic conjugated 1,3-dienes; and interpolymers of at least 50% byweight of an acyclic conjugated 1,3-diene, up to 50% by weight of ahydrocarbon monomer selected from the group consisting of styrene,alpha-methyl styrene and ring-alkyl substituted styrenes, and up to 10%by weight of a vinylidene monomer having a polar substituent saidnon-polar hydrocarbon elastomer normally being incompatible with saidrigid vinyl chloride polymer;.sai'd' composition also containing fromabout l-10% by weight of graft copolymer prepared by polymerizing 10-200parts by weight of a monovinylidene aromatic hydrocarbon and a nitrileselected from the group consisting of acrylonitrile, methacrylonitrileand mixtures thereof in the presence of 100 parts by weight of a rubberydiene polymer having a second order transition temperature below about 0C., said graft copolymer being suificient to enhance the compatibilityof the rigid vinyl chloride polymer and the non-polar hydrocarbonelastomer.

3. A method for preparing an intimate fusion blend of a rigid vinylchloride polymer and a non-polar hydrocarbon elastomer that is normallyincompatible with said rigid vinyl chloride polymer which comprisescomalaxating 10-98 parts by weight of a rigid vinyl chloride polymer,said vinyl chloride polymer comprising at least 80% by weight vinylchloride and correspondingly -2 parts by weight of a non-polarhydrocarbon elastomer selected from the group consisting of homopolymersof alphamonoolefines; interpolymers of at least two alpha-monoolefines;interpolymers of at least 85 by weight of an alpha-monoolefine and up to15% by weight of an interpolymerizable vinylidene monomer; homopolymersof acyclic conjugated 1,3-dienes; and interpolymers of at least 50% byweight of an acyclic conjugated 1,3-diene, up to 50% by weight of ahydrocarbon monomer selected from the group consisting of styrene,alpha-methyl styrene, and ring-alkyl substituted styrenes, and up to 10%by weight of a vinylidene monomer having a polar substitucut, with fromabout 110% by weight of graft copolymer prepared by polymerizing 10-200parts of a monomer mixture of a monovinylidene aromatic hydrocarbon anda nitrile selected from the group consisting of acrylonitrile,methacrylonitrile and mixtures thereof in the presence of parts byweight of a rubbery diene polymer having a second order transitiontemperature below about 0 C., said comalaxating temperature above thefusion point of the rigid vinyl chloride polymer.

7 4. A composition as in claim 1 in which the graft copolymer isstyrene-acrylonitrile-polyhutadiene.

5. A composition as in claim 1 in which the nonpolar hydrocarbonelastomer comprises mixtures of homopolymers and interpolymers of alpha-monoolefines.

6. A composition as in claim 1 in which the nonpolar hydrocarbonelastomer comprises mixtures of homopolymers and interpolymers ofacyclic conjugated 1,3-dienes.

7. A composition. as in claim 2 in which the graft c0- polymer isstyrene-acry1onitrile-polybutadiene.

8. A composition in claim 2 in which the nonpolar elastomer comprisesmixtures of homopolymers and interpolymers of alpha-monoolefines.

9. A composition as in claim 2 in which the nonpolar elastomer comprisesmixtures of homopolymers and interpolymers of acyclic conjugated1,3-dienes.

References Cited by the Examiner UNITED STATES PATENTS 2,658,0501:1/1953- Signer et al. 260-237 2,755 ,270 7/ 1956 Hayes 260-8762,802,808 8/ 1957 Hayes 260-876 2,802,809 8/1957 Hayes 260-876 3,118,8541/1964 Hess et a1 260876 MURRAY TILLMAN, Primary Examiner. GEORGE F.LESMES, Assistant Examiner.

1. A COMPOSITION OF MATTER COMPRISING AN INTIMATE FUSION BLEND OF 10-98PARTS BY WEIGHT OF A RIGID VINYL CHLORIDE POLYMER, SAID VINYL POLYMERCOMPRISING AT LEAST 80% BY WEIGHT VINYL CHLORIDE AND CORRESPONDINGLY,90-2 PARTS BY WEIGHT OF A NON-POLAR HYDROCARBON ELASTOMER SELECTED FROMTHE GROUP CONSISTING OF HOMOPOLYMERS OF ALPHA-MONOOLEFINES,INTERPOLYMERS OF AT LEAST TWO ALPHAMONOOLEFINES; INTEROPOLYMERS OF ATLEAST 85% BY WEIGHT OF AN ALPHA-MONOOLEFINE AND UP TO 15% BY WEIGHT OFAN INTERPOLYMERIZABLE VINYLIDENE MONOMER; HOMOPOLYMERS OF ACYCLICCONJUGATED 1,3-DIENE; AND INTERPOLYMERS OF AT LEAST 50% BY WEIGHT OF ANACYLIC COMJUGATED 1,3DIENE, UP TO 50% BY WEIGHT OF A HYDROCARBON MONOMERSELECTED FROM THE GROUP CONSISTING OF STYRENE, ALPHA-METHYL STYRENE ANDRING-ALKYL SUBSTITUTED STYRENES, AND UP TO 10% BY WEIGHT OF A VINYLIDENEMONOMER HAVING A POLAR SUBSTITUENT, SAID NON-POLAR HYDROCARBON ELASTOMERNORMALLY BEING INCOMPATIBLE WITH SAID RIGID VINYL CHLORIDE POLYMER; SAIDCOMPOSITION ALSO CONTAINING FROM ABOUT 1-10% BY WEIGHT OFGRAFT-COPOLYMER PREPARED BY POLYMERIZING 10-200 PARTS BY WEIGHT OF AMONOVINYLDIENE AROMATIC HYDROCARBON AND A NITRILE SELECTED FROM THEGROUP CONSISTING OF ACRYLONITRILE, METHACRYLONITRILE AND MIXTURESTHEREOF IN THE PERESENCE OF 100 PARTS BY WEIGHT OF A RUBBERY DIENEPOLYMER HAVING A SECOND ORDER TRANSITION TEMPERATURE BELOW ABOUT 0*C.,SAID GRAFT COPOLYMER BEING SUFFICIENT TO ENHANCE TO COMPATIBILITY OF THERIGID VINYL CHLORIDE POLYMR AND THE NON-POLAR HYDROCARBON ELASTOMER.